1. Field
The present invention relates to bump pitches in flip-chip integrated circuit devices.
2. Background
Flip-chip integrated circuit (IC) devices include an IC die that is bonded to a substrate through one or more sets of solder bumps. The substrate facilitates interconnection between the IC die and a printed circuit board (PCB) on which the substrate is mounted. Through the PCB, the IC device can be coupled to a number of other devices mounted on the PCB.
Lead-based solder bumps offer advantages in bonding an IC die to a substrate. For example, lead-based solder bumps are relatively flexible and have well-defined melting points. As such, lead-based solder bumps are well-suited to absorb stresses caused by coefficient of thermal expansion (CTE) mismatches between the IC die and the substrate.
Nevertheless, lead-based solder bumps, like many lead-based products, have negative environmental effects. Thus, a trend has developed in which lead-based elements are removed from many products, including IC devices. This trend has resulted in a migration from lead-based solder bumps to lead-free solder bumps. These lead-free solder humps, however, are often not able to absorb stress caused by CTE mismatch, often resulting in the solder bumps cracking when the IC die and the substrate are bonded.